Management of common GUI colors in OpenFLUID-Builder

* Added reference colors in config file
* Updated stylesheets

(references OpenFLUID/openfluid#246)
Fix of recent projects management In OpenFLUID-Builder

* Fixed add of current project in recent projects
* Updated referesh of recent projects in home module
* Cleaned code

(references OpenFLUID/openfluid#246)
Fix of model updated variables in OpenFLUID-Builder

* Fixed model view
* Fixed model signature

(references OpenFLUID/openfluid#246)
CMake macro for building OpenFLUID-Builder extensions

* Added macros in helpers
* Added tests for configuration and build of Builder extensions
* Cleaned code and CMake config files
Enhancement of the signal exchanges in OpenFLUID-Builder

* Added qualification to signals when FluidX descriptors are modified,
  giving more information about the modified part
* Cleaned code

(references OpenFLUID/openfluid#246)
Add landr method documentation
 * Updated documentation
Merge branch 'add-landr-methods-documentation' of https://github.com/rabotin/openfluid into rabotin-add-landr-methods-documentation